Valve train for an internal combustion engine

ABSTRACT

The present disclosure describes a valve train for an internal combustion engine. The valve train includes a camshaft with a first cam and a second cam, a rocker lever assembly with a shifting pin that is adjustable in an axial direction between at least two positions, a cam follower mounted on the shifting pin, an adjusting device for adjusting a control pin arranged in the shifting pin, and a guide contour arranged on the camshaft having a first guide track and a second guide track intersecting the first guide track in an X-like manner. The control pin engages into the guide tracks and adjusts the shifting pin to adjust the cam follower. The adjusting device includes a control rod that is shiftable parallel to the shifting pin and contacts the control rod.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to German Application No. DE 10 2019204 589.8 filed on Apr. 1, 2019, the contents of which are herebyincorporated by reference in its entirety.

TECHNICAL FIELD

The present invention relates to a valve train for an internalcombustion engine having a camshaft with a first and a second camarranged adjacent thereto. The invention additionally relates to aninternal combustion engine having such a valve train.

BACKGROUND

From DE 10 2017 205 571 A1 a generic valve train for an internalcombustion engine having a camshaft with a first and a second camarranged axially adjacent thereto is known. The known valve traincomprises a rocker lever assembly that is adjustable in the axialdirection between at least two positions, on which a cam follower, herea cam roller, is mounted. In the shifting pin itself, an adjustablecontrol pin of an adjusting device is arranged.

Through the adjusting device, the cam follower can be adjusted betweenits two positions and thereby influence, in particular switch on orswitch off a corresponding cylinder of the internal combustion engine.The known adjusting device comprises a first adjustable control pin anda second adjustable control pin which in each case interact with a guidetrack arranged on the camshaft. However, because of the known adjustingdevice with two control pins and the two separate guide tracks, theentire adjustment of the valve train is only possible in a comparativelyinvolved manner.

SUMMARY

The present invention therefore deals with the problem of stating animproved or at least an alternative embodiment for a valve train of thegeneric type, which is characterized in particular by a simplifiedconstruction.

According to the invention, this problem is solved through the subjectof the independent claim(s). Advantageous embodiments are subject of thedependent claims.

With a valve train known per se, the present invention is based on thegeneral idea of providing a guide contour having two guide tracksintersecting one another X-like, by way of which for the adjustmentmerely a single adjustable control pin is required. The valve trainaccording to the invention for an internal combustion engine comprises acamshaft having at least one first cam and a second cam arranged axiallyadjacent thereto, and a rocker lever assembly having a shifting pin thatis adjustable in the axial direction between at least two positions, onwhich a cam follower, for example a cam roller, is mounted. In thiscase, a cam roller would be mounted for example axially fixed androtatable on the shifting pin. In the shifting pin itself, a control pinthat is adjustable radially to the shifting pin by means of an adjustingdevice is arranged. According to the invention, the guide contourarranged on the camshaft is now equipped with a first guide track and asecond guide track intersecting the same X-like. Here, the control pinoptionally engages in the first or the second guide track and therebyadjusts the shifting pin between its two positions. In a first positionof the shifting pin, the cam follower interacts with the first cam andin a second position of the shifting pin with the second cam. By way ofdifferent cam profiles, an influencing of valve opening times can takeplace or a switching-off of a cylinder. The adjusting device comprises acontrol rod that is shiftable parallel to the shifting pin with a firstswitching region, a second switching region and a neutral regionarranged in the axial direction of the control rod in between, whereinthe control pin upon contact with the first control region is adjustableinto the first guide track and upon contact with the second controlregion into the second guide track. With the valve train according tothe invention it is thus possible to merely provide a single control pinon the shifting pin and with the same together with the guide contouraccording to the invention bring about the adjusting of the shiftingpin. Through the merely one single required control pin it is possibleto build the shifting pin shorter in the axial direction andadditionally reduce the parts variety and connected with this also thestorage and logistical costs as well as the assembly expenditure. Byproviding the guide contour according to the invention with twointersecting guide tracks, the guide contour as a whole can also bebuilt in a more compact and thus more space-saving manner. Altogether,an adjustable valve train can thus be realised which compared with thevalve train known from the prior art is formed less expensive in design,more cost-effective and in particular also requires less installationspace.

In an advantageous further development of the solution according to theinvention, the adjusting device comprises a housing in which the controlrod is guided and in particular also mounted. Such a housing can beformed cylindrically for example and comprise a shell opening, via whichthe control pin is contactable with the control regions. Such acylindrical housing offers a particularly installation space-optimisedsolution provided the control rod is arranged coaxially in the housing.By way of the shell opening on the housing, a protected arrangement ofthe control rod and in particular also of an adjusting mechanismrequired for the adjustment of the control rod in the housing can beachieved, provided that in particular the shell opening faces downwardfor example, so that in particular oil impinging on the housing shell onthe outside cannot enter the housing.

In an advantageous further development of the solution according to theinvention, a solenoid, in particular a coil surrounding the control rod,and a permanent magnet arranged on the control rod are provided, whereinthe control rod is adjustable in its first or second position byenergising the solenoid. By means of such a solenoid, a cost-effectiveand extremely exact and low-maintenance actuation device for actuatingthe control rod and thus for actuating the adjusting device can beachieved. Through the coaxial arrangement of the solenoid, in particularof the coil and of the permanent magnet arranged on the control rod, aninstallation space-optimised solution can be additionally created, whichis additionally arranged protected in the housing.

In an advantageous further development of the solution according to theinvention, at least one spring is provided which preloads the controlrod into its first or second position. In this case, a solution is thusconceivable with which for example the previously described solenoid byenergising brings about an adjusting of the control rod into its firstposition, while a resetting is exclusively effected by means of thespring. By way of this, it can also be achieved that upon a failure ofthe solenoid a position of the control rod that is predefined by thespring and thus a predefined cam following is defined. Alternatively itis obviously also conceivable that two solenoids, in particular twocoils surrounding the control rod and two permanent magnets arranged onthe control rod are provided, wherein the control rod throughalternative energisation of the solenoids is adjustable into its firstor second position. Although such a solution is more expensive than asolution with a single solenoid and a spring, it can however bring abouta quicker shifting under certain conditions.

In an advantageous further development of the solution according to theinvention, the first control region is arranged on the longitudinal endside of the control rod and formed pot-shaped, wherein the spring isformed as a coil spring and is at least partly arranged in the firstcontrol region. In this case, the spring supports itself at the one endin the first control region and at the other end for example on ahousing. This causes a protected arrangement of the spring not only inthe housing but additionally at least partly also in the first controlregion, as a result of which a veritable encapsulation of the spring andthus a particularly protected arrangement of the same can be achieved.

Practically, a position sensor is provided via which a position of thecontrol rod and thus indirectly also a position of the shifting pin orof the valve train can be detected. Such a position sensor can be formedfor example as a Hall sensor. In particular it is conceivable here thatsuch a position sensor monitors the position of the first or secondcontrol region.

Practically, the first and/or second control region has/have a flattenedregion which is designed as contact region to the control pin. By way ofthis, an areal contact with the control pin can be achieved as a resultof which not only a punctiform but an areal distribution of the forcetransmission between control region and control pin is made possible andbecause of this wear manifestations in particular can be minimised.

In a further advantageous embodiment of the solution according to theinvention, the first and the second control region have differentdiameters. By way of this it is possible in particular to comparativelyeasily compensate for different cam strokes.

Furthermore, the present invention is based on the general idea ofequipping an internal combustion engine with such a valve train and byway of this transfer the previously described advantages of the valvetrain to the internal combustion engine.

Further important features and advantageous of the invention areobtained from the subclaims, from the drawings and from the associatedfigure description by way of the drawings.

It is to be understood that the features mentioned above and still to beexplained in the following cannot only be used in the respectivecombination stated but also in other combinations or by themselveswithout leaving the scope of the present invention.

Preferred exemplary embodiments of the invention are shown in thedrawings and are explained in more detail in the following description,wherein same reference numbers relate to same or similar or functionallysame components.

BRIEF DESCRIPTION OF THE DRAWINGS

It shows, in each case schematically,

FIG. 1 a valve train for an internal combustion engine according to theinvention in a view with sectioned adjusting device,

FIG. 2 a sectional representation through the adjusting device accordingto FIG. 1,

FIG. 3 a representation as in FIG. 2, however with another embodiment,

FIG. 4 a view of a control rod with two control regions according to theinvention,

FIGS. 5A to 5D illustrate different control positions of the adjustingdevice.

DETAILED DESCRIPTION

According to FIG. 1, a valve train 1 according to the invention for aninternal combustion engine 2 which is not shown in more detail comprisesa camshaft 3 with a first cam 4 and a second cam 5 arranged axiallyadjacent thereto. Likewise provided is a rocker lever assembly 6 with ashifting pin 8 that is adjustable in the axial direction 7 between atleast positions, on which a cam follower 9, in particular a cam roller10, is mounted. Likewise provided are an adjusting device 11 (see alsoFIGS. 2, 3 and 5) and an adjustable control pin 12, which is arranged inthe shifting pin 8, in particular radially mounted in the same.According to the invention, a guide contour 13 having a first guidetrack 14 and a second guide track 15 intersecting the same X-like is nowarranged on the camshaft 3. Here, the control pin 12 optionally engagesinto the first or second guide track 14, 15 (according to FIG. 1, intothe first guide track 14) and thereby adjusts the shifting pin 8 withthe cam followers 9 arranged thereon between its/their two positions,wherein the cam follower 9, here the cam roller 10, in a first positionof the shifting pin 8, interacts with the first cam 4 and in the secondposition of the shifting pin 8 with the second cam 5. According to FIG.1, the rocker lever assembly 6 comprises two cam followers 9, both ofwhich are coaxially rotatably arranged on the shifting pin 8 and each ofwhich interacts either with an associated first cam 4 or an associatedsecond cam 5.

In addition to this, the adjusting device 11 comprises a control rod 16(see also FIG. 4) that is shiftable parallel to the shifting pin 8, i.e.in the axial direction 7, with a first control region 17, a secondcontrol region 18 and a neutral region 19 arranged in the axialdirection in between. Upon a contact with the first control region 17,the control pin 12 is adjusted into the first guide track 14 while upona contact with the second control region 18 it is adjusted into thesecond guide track 15. In the neutral region 19, the control pin 12 isneither in contact with the first control region 17, nor with the secondcontrol region 18 (see FIGS. 5a and 5c ), as a result of which noactuation of the control pin 14 by the adjusting device 11 takes place.With the adjusting device 11 according to the invention it is possiblethat in the shifting pin 8 merely a single control pin 12 has to bearranged, as a result of which a solution that is significantly lessexpensive in design with a lower number of parts and with a lowerassembly expenditure can be achieved. Through the guide contour 13according to the invention with the guide tracks 14, 15 intersectingX-like, a guide contour 13 can be additionally also created which isinstallation space-optimised in particular in the axial direction andbecause of this requires little space. Altogether, a solution that issimple in design and installation space-optimised can thus be createdwith the valve train 1 according to the invention.

Viewing FIGS. 1 to 5 further it is noticeable that the adjusting device11 comprises a housing 20 in which the control rod 16 is guided ormounted. In the present case, the housing 20 is cylindrical in designand comprises a shell opening 21, via which the control pin 12 can enterinto contact with the control regions 17, 18. The shell opening 21 canbe arranged centrally on the adjusting device 11 or on one side at anend of the housing 20. Here, the control rod 16 is comparatively easy toproduce, for example by turning or thermal joining of the two controlregions 17, 18 on the control rod 16, as a result of which an adjustingdevice 11 that is simple in design and thus cost-effective can becreated. The circumstance that the adjusting device 11 in the installedstate (see FIG. 1) is arranged in such a manner that the shell opening21 faces downwards, the control rod 16 is also arranged protected withinthe housing 2 since in particular oil striking the housing 20 cannotenter the same.

For actuating or adjusting the control rod 16 with the control regions17, 18 arranged thereon a solenoid 22, in particular in the manner of acoil surrounding the control rod (16) (see FIG. 2) or in the manner of acoil surrounding the second control region 18 (see FIG. 3) is provided,wherein in addition according to FIG. 3 a permanent magnet 23 isarranged on the control rod 16. This permanent magnet 23 can obviouslybe integrated in the control rod 16 in another manner, as is shown forexample according to FIG. 2. Purely theoretically, the control rod 16can also consist of a magnetisable material and thereby be subjected tothe forces required for adjusting the control rod 16 by the solenoid 22.

Viewing FIGS. 1 to 3 it is noticeable that at least one spring 24 isprovided, which preloads the control rod 16 and thereby also the twocontrol regions 17, 18 into its first or second position, here into itssecond position. By means of such a spring 24, a failsafe function canbe realised in particular, which enforces a predefined position of thecontrol rod 16 upon a failure of the solenoid 22 or generally upon afailure of an actuation device for adjusting the control rod 16.Alternatively to the spring 24, a further solenoid 22 can obviously beprovided so that in this case a total of two solenoids 22 are provided,which upon corresponding energisation, adjust the control rod 16 intoits first or second position.

Viewing FIGS. 1 to 5 it is noticeable that the first control region 17is arranged on the longitudinal end side of the control rod 16 and atthe same time formed pot-like, wherein the spring 24, which in thepresent case is embodied as a coil spring, is at least partly arrangedin the first control region 17. By way of this, a protected arrangementof the spring 24 can be achieved in the housing 20 and in the directionof the shell opening 21 a protected arrangement over the first controlregion 17 can be achieved. A position sensor 25, for example a Hallsensor, via which a position of the control rod 16 and thus a positionof the two control regions 17, 18 is detectable can likewise beprovided. By way of this, the exact control position can be transmittedfor example to a motor control in each case.

The first and/or the second control region 17, 18 can be embodied ascylindrical control discs. In order to improve a contact between thecontrol pin 12 and the respective control region 17, 18, it can beadditionally mooted that the first and/or the second control region 17,18 comprises a flattened region 26 which serves as contact region forthe control pin 12.

Viewing now the individual control positions of the adjusting device 11according to the invention as per FIGS. 5A to 5D it is evident thataccording to FIG. 5a the actuator, i.e. in the present case the controlrod 16, is retracted and the control pin 12 projects into the neutralregion 19, in which no actuation of the same through the adjustingdevice 11, i.e. the first or second control region 17 or 18 takes place.According to FIG. 5b the adjusting device 11 is now activated. Forexample by energising the solenoid 22, as a result of which the controlrod 16 has shifted to the left and the control pin 12 enters intocontact with the second control region 18. By way of this, the controlpin 12 is moved downwards and thereby adjusted into the second guidetrack 15, in the control pin 12 now runs and is shifted in the axialdirection 5 to the left into the neutral region 19 by means of the guidetrack 15, as shown according to FIG. 5c . According to FIG. 5d , thecontrol rod 16 is again moved to the right as a result of which thecontrol pin 12 now enters into contact with the first control region 17,upon which the same adjusts the control pin 12 into the first guidetrack 14. Altogether it is evident from FIG. 5a to d that the path ofthe control rod 16 required for changing over from the first to thesecond cam 4, 5 or back is comparatively short, which likewisecontributes towards minimising the installation space. In addition tothis merely a single adjusting device 11 or a control pin 12 and a guidecontour 13 for each cylinder is required with the valve train 1according to the invention. As is evident, furthermore, from FIGS. 1 to5, the two control regions 17, 18 have different diameters in order tothereby compensate for different cam strokes.

With the valve drive 1 according to the invention and the internalcombustion engine 2 equipped with such according to the invention, asolution that is simple in design, cost effective and additionallyinstallation space-optimised for changing over between different camprofiles can thus be achieved.

1. A valve train for an internal combustion engine, comprising: acamshaft with a first cam and a second cam arranged adjacent thereto, arocker lever assembly with a shifting pin that is adjustable in an axialdirection between at least two positions, on which a cam follower ismounted, an adjusting device for adjusting a control pin arranged in theshifting pin, a guide contour arranged on the camshaft having a firstguide track and a second guide track intersecting the first guide trackin an X-like manner, the control pin engages into the first guide trackor the second guide track and adjusts the shifting pin between the atleast two positions, so that the cam follower in a first position of theshifting pin interacts with the first cam and in a second position ofthe shifting pin interacts with the second cam, and the adjusting deviceincluding a control rod that is shiftable parallel to the shifting pinhaving a first control region, a second control region and a neutralregion arranged in between in the axial direction, wherein the controlpin upon contact with the first control region is adjusted into thefirst guide track and upon contact with the second control region isadjusted into the second guide track.
 2. The valve train according toclaim 1, wherein the adjusting device further includes a housingstructured and arranged to guide the control rod.
 3. The valve trainaccording to claim 1, wherein at least one of the first control regionand the second control region is structured as a cylindrical shiftingdisc.
 4. The valve train according to claim 2, wherein the housing isstructured cylindrically and comprises a shell opening, via which thecontrol pin is contactable with the first control region and the secondcontrol region.
 5. The valve train according to claim 1, furthercomprising a solenoid arranged on the control rod, wherein the controlrod is adjustable into the first position or the second position byenergising the solenoid.
 6. The valve train according to claim 1,further comprising two solenoids, wherein the control rod is adjustableinto the first position or the second position through alternativeenergising of the two solenoids.
 7. The valve train according to claim1, further comprising at least one spring, structured and arranged topreload the control rod into the first position or the second position.8. The valve train according to claim 7, wherein the first controlregion is arranged on a longitudinal end side of the control rod and hasa pot-like shape, and wherein the at least one spring is structured as acoil spring and is at least partly arranged in the first control region.9. The valve train according to claim 1, further comprising a positionsensor, structured and arranged to detect a position of the control rod.10. The valve train according to claim 1, wherein at least one of: atleast one of the first control region and the second control region hasa flattened region that provides a contact region for the control pin,and the first control region and the second control region have at leastone of different heights and different diameters from one another. 11.An internal combustion engine comprising: a valve train, the valve trainincluding: a camshaft with a first cam and a second cam arrangedadjacent thereto; a rocker lever assembly with a shifting pin that isadjustable in an axial direction between at least two positions, onwhich a cam follower is mounted; an adjusting device for adjusting acontrol pin arranged in the shifting pin; a guide contour arranged onthe camshaft having a first guide track and a second guide trackintersecting the first guide track in an X-like manner; the control pinengages into the first guide track or the second guide track and adjuststhe shifting pin between the at least two positions, so that the camfollower in a first position of the shifting pin interacts with thefirst cam and in a second position of the shifting pin interacts withthe second cam; and the adjusting device including a control rod that isshiftable parallel to the shifting pin a first control region, a secondcontrol region and a neutral region arranged in between in the axialdirection, wherein the control pin upon contact with the first controlregion is adjusted into the first guide track and upon contact with thesecond control region is adjusted into the second guide track.
 12. Theinternal combustion engine according to claim 11, wherein the adjustingdevice further includes a housing structured and arranged to guide thecontrol rod.
 13. The internal combustion engine according to claim 12,wherein the housing has a cylindrical shape with a shell opening, andwherein the control pin contacts the first control region and the secondcontrol region via the shell opening.
 14. The internal combustion engineaccording to claim 11, further comprising a solenoid structured andarranged to adjust the control rod into at least one of the firstposition and the second position.
 15. The internal combustion engineaccording to claim 11, further comprising at least one spring structuredand arranged to preload the control rod into at least one of the firstposition and the second position.
 16. The internal combustion engineaccording to claim 11, wherein at least one of the first control regionand the second control region has a flattened region that provides acontact region for the control pin.
 17. The internal combustion engineaccording to claim 11, wherein the first control region and the secondcontrol region have different heights from one another.
 18. The internalcombustion engine according to claim 11, wherein the first controlregion and the second control region have different diameters from oneanother.
 19. The valve train according to claim 5, wherein the solenoidincludes a coil surrounding the control rod.
 20. The valve trainaccording to claim 5, wherein the solenoid includes a permanent magnetarranged on the control rod.